Physiological Effects Of Seed Priming And Coating On Germination Of Seed And Stress Tolerance Of Seedlings In Rice(Oryza Sativa L.)

The effects of priming treatments (CaCI2 , CaCI2+ NaCI (1:1.4 mol/mol), CaCI2 + NaC! (1:1.4 mol/moO+10, 100, or 1000 ppm GA3 at-1.25 MPa for 2 d and polyethylene glycol (PEG 8000) at -1.25 MPa for 3 d at 20 癈) were investigated on rice seeds (Oryza sativa L. cv 'Zhenongda 454') in germination tests in the laboratory. Priming did not improve rice seed germination, but significantly increased germination energy and germination index, and slightly reduced mean germination time (MGT). Seeds primed with salt solutions had a significantly higher germination index and lower MGT than those primed with PEG8000. There were no significant differences in energy of germination and germination percentage among seeds primed with salt solutions and those primed with PEG8000. The addition of GA3 to CaCI2 + NaCI solution did not significantly improve the rate of germination or germination percentage as compared with CaCI2 + NaCI priming solution. In a greenhouse trial, priming improved the seedling vigour index and seedling and stand establishment in flooded soil. The addition of GA3 to CaCI2 + NaCI did not significantly increase either the speed of emergence or stand establishment as compared with CaCI2 + NaCI priming solution. It is suggested that priming of rice seeds may contribute to improved seedling establishment in anearobic soil.The effects of priming treatments (CaCI2, NaCI, KNO3, and polyethylene giycol (PEG 8000) at -1.25 MPa for 2, 3, or 4 d at 20癈) were evaluated on microorganism growth on rice seeds (Oryza sativa L cv 'Zhenongda 454') under conditions of 20癈and near ultra violet (NUV). The results showed that priming caused the increase in number of genera or species of fungi deteced in rice seeds. Compared with control, priming had no significant effect on the total infestation of rice seed. Primed seeds had significantly higher incidenceof Fusarium spp. and lower incidence of Cladosporium spp. than nonprimed ones. Pre-treatment with sodium hyperchlorite had no effects on the total infestation of rice seed. Pre-treatment caused decrease in the incidence of Fusarium spp. in primed rice seeds and increase in the incidence of Curvularia spp.Seeds of two hybrid rice combinations, Shanyou 10 and Eryoupeijiu , were treated with four priming slutions, H2O, H2O+10 mM Proline, 150 mM NaCI and 150 mM NaCI+10 mM Proline.for 36 h at 25癈. Non-primed or primed seeds were germinated in 4 solutions, H2O,50mM, 100mM or 150mM NaCI solutions, for 10 d at 30癈.Content of compatible solutes,?praline, total soluble sugar, fructose and sucrose in seeds or stressed seedlings wasdetermined. The results showed that significant higher levels of proline and sucrose and lower levels of total soluble sugar and fructose in primed seeds were observed as compared with control (non-primed seeds). Priming evidently increased the content of total soluble sugar, fructose and sucrose ,and decreased the content of proline in stressed seedlings. Priming also improved the tolerance index and tolerance ratio of seedlings in hybrid rice. A significant positive correlation between tolerance index and tolerance ratio of seedlings in hybrid rice and content of proline in primed seeds and content of fructose and sucrose in stressed seedlings was observed, but a significant negative correlation between tolerance index and tolerance ratio of seedlings and content of proline in primed seeds was found. The content of total soluble sugar in stressed seedlings was only positively correlated with tolerance ratio of seedlings. A significant negative correlation between content of fructose in primed seeds and content of total soluble sugar and fructose in stressed seedlings was also found. Therefore, priming stimulated utilization of fructose in seeds , and resulted in decreased content of fructose in seeds, and then increased content of fructose in stressed seedlings, thus improved salt-tolerance of seedlings in hybrid rice. It is suggested that this may be an internal phsiological regulation mechanism that priming improved salt-toleran...